A combustion engine is an apparatus for generating mechanical energy by burning fuel. Combustion engines may be used, for example, to drive motor vehicles such as motor cars, motor bikes, generators for generating electric power, pumps, and a vast variety of other devices. A combustion engine has at least one combustion chamber in which fuel needs to be injected and ignited in accordance with the position of a piston or other moving member of the engine.
In a capacitive discharge ignition (CDI) system, an ignition spark may be produced in a combustion chamber by discharging a capacitor via a first coil that has only a small number of turns. The first coil may be magnetically coupled to a second coil that has a greater number of turns than the first coil. The relatively low voltage applied to the first coil by the capacitor may thus be transformed into a much higher voltage which produces the spark and thus ignites the fuel.
In an inductive discharge ignition (IDI) system, in contrast, the capacitor may be absent. Instead, the first coil may be “charged” with an electric current. Interrupting this current may generate a voltage peak across the second coil which produces the spark and thus ignites the fuel. Electronic fuel injection (EFI) systems are more commonly implemented using inductive discharge ignition because both inductive discharge ignition and other actuators used on EFI systems require a steady supply of power. By contrast, CDI systems can progressively store power on the ignition capacitor and may be used with fuel delivery from a carburetor rather than electronic actuators. The accumulation of energy on the capacitor allows them to work both with a steady supply of power from a battery (known as “d.c. CDI”) or intermittent pulses of power from an alternator (known as “a.c. CDI”). In both cases a switch Mode Power Supply can be beneficially employed to create a significant voltage, typically 150V-350V, on the ignition capacitor.